Comparison between four integer ambiguity resolved PPP GNSS time transfer software solutions

Abstract We present a comparison between four different software solutions (dubbed PPP-AR or IPPP, all based on the resolution of integer ambiguities of the carrier-phase) that compute time links between GNSS receivers. Additional processing layers have been specially developed to enable usage for time transfer purposes. A variety of GNSS receivers connected to UTC(k) timescales across the globe, covering a wide range of baselines and several GNSS receiver models was used in this work. For one of the links, the availability of an optical fiber link between the stations allowed a comparison of each software-based GNSS link to this common reference, otherwise links were compared with each other using a specially-developed four-cornered hat algorithm. In the performance analysis we focused on the frequency stability of the time links. Results show that all four independently developed software solutions agree within 20 ps on TDEV for all averaging times and highlight the importance of mitigating day-boundary phase discontinuities. This demonstrates the reliability of the different implementations of the PPP-AR/IPPP technique for operational time transfer.